Adjustable catheter assembly

ABSTRACT

The invention relates to a catheter assembly comprising a cannula, needle and catheter inserter wherein the inserter is in slidable relationship to the cannula and wherein the inserter or other device also serves to selectively restrict the cannula and needle from sliding relative to the inserter. The restricted movement is caused by a portion of the cannula swelling when contacted by a liquid. The invention also relates to a method of inserting a cannula into a living subject using an inserter which is positioned such that the desired length of cannula for initial insertion extends beyond the inserter. The method also relates to further inserting the cannula into the living subject after initial insertion of the cannula.

BACKGROUND OF THE INVENTION

(a) The Invention

The invention relates to a catheter assembly and a method for insertinga cannula useful for the introduction of nutrients or medication, or theextraction of fluids from a living subject. The catheter assembly moreparticularly comprises a cannula, needle and catheter inserter whichallows the selection of the desired length of cannula to be inserted.The method particularly relates to a method of inserting a cannula intoa living subject to a desired length.

(b) Background Information

A number of catheter assemblies are known for introduction of apolymeric cannula into a vein, artery or cavity of a living subject forinfusion or extraction of fluids.

In one method, a steel needle is sized to fit within the duct of acannula and is inserted from the proximal end of the cannula so that theneedle exits the distal end. The needle is then inserted into the livingsubject after which the needle is removed from the cannula, leaving thecannula behind with at least its distal end in the subject. Additionaltubing can be attached thereto or medicaments or nutrients can be causedto flow through the cannula into the subject.

In order to prevent the needle from sliding relative to the cannula oninsertion, several catheter inserters have been developed which aid theperson inserting the cannula to prevent such sliding. This also providesa way to control the cannula without contaminating it. Inserters of atype comprising a positionally fixed device having a pair of wingedmembers which when folded up will pinch the needle and prevent motion ofthe needle relative to the cannula and catheter inserter are known.Generally a relatively stiff cannula of a material to be inserted intothe subject such as TEFLON (from DuPONT) is fixed to the distal end ofthe inserter, while a flexible tubing (e.g. polyvinyl chloride) isattached to the proximal end of the inserter in flow communication withthe cannula.

For example, in U.S. Pat. No. 4,194,504 a winged catheter inserter fixedto a cannula is described comprising a resilient tubular body having alumen and a pair of wings having substantially uniform thickness suchthat on folding up of the wings, the lumen changes shape to capture theneedle within for easier insertion. See also U.S. Pat. Nos. 4,198,973;4,192,304; 4,192,305; 4,300,553; 4,388,074; 4,445,893; 4,353,369; and4,326,519.

A difficulty with this type of winged inserter is that the length ofcannula to be inserted is limited. The length is predetermined by theposition that the inserter has been fixed on the cannula material. Thewinged inserters of the prior art have been attached to the cannula fora number of reasons including the need to secure cannula at one end ofthe inserter and flexible tubing at the other end and to prevent therelative movement of the inserter after use. Relatively long lengths ofcannula cannot be used with this type of inserter because the insertermust be affixed relatively close to the distal end for accurate controlof the cannula and only that portion extending from the distal end ofthe inserter may be used. Another difficulty with the fixed winginserter is the desirability of being able to differ the length of theneedle and the cannula for ease of insertion into the subject. A personinserting such cannulae, such as a nurse or doctor, will have varyingpreferences as to the positioning of the inserter relative to the needleand cannula end. This requires stocking several different sizes ofcannula fabricated with differing distal end lengths.

One method of overcoming the difficulty of inserting a variable orrelatively long length of cannula (greater than about 50 mm) has been toselect a needle with an inner diameter greater than the outer diameterof the cannula. The needle is inserted into the subject and the cannulais fed through the needle into the subject to the desired length. Thistechnique has several difficulties. First, the cannula for insertionmust be stiff and/or have a wire running through its duct duringinsertion. Also, when inserting such a device into an area such as ablood vessel, removal of the needle allows blood to escape around theinsertion site or possible infection to enter through the insertion sitewhich is larger than the cannula. After the cannula is in the desiredposition, the needle is generally removed. There is difficulty inremoving the needle without further escape of blood or chance ofinfection. This is especially true when the cannula is attached to a hubportion which prevents sliding the needle off of the cannula's proximalend. If the needle is allowed to remain on the cannula there can bedifficulty in preventing the sharpened edge of the needle from furtherpiercing the subject or piercing the cannula. Bulky containmentmechanisms are used to minimize but not eliminate this danger. Thealternative to this type of method is direct surgical implantation of acannula in the desired area which is both traumatic and costly.

In summary the prior art to date has encountered great long standingdifficulty in inserting a desired length of cannula initially orrelatively long lengths of cannula after insertion of the distal end ofa cannula. The present invention is directed to overcoming one or moreof the problems as set forth above.

SUMMARY OF THE INVENTION

One aspect of the invention relates to a catheter assembly comprising:

a cannula having a distal end portion, a proximal end portion, and alongitudinal duct therethrough from the distal end portion to theproximal end portion;

a needle having a distal and a proximal end and having a sharpenedinsertion tip at the distal end, the needle being positioned within thedistal end portion of the longitudinal duct of the cannula with theinsertion tip extending beyond the distal end of the cannula; and

a catheter inserter having inserter distal and proximal ends and havinga cannula guide channel extending from the inserter distal end to theinserter proximal end, the cannula being positioned in slidablerelationship through the channel such that the distal end portion of thecannula extends beyond the distal end of the channel; and

a means for selectively restricting the cannula and needle from slidingrelative to the channel.

Another aspect of the invention relates to a method comprising:

(a) selecting a catheter assembly comprising:

a cannula having a distal end portion, a proximal end portion, and alongitudinal duct therethrough from the distal end portion to theproximal end portion;

a needle having a distal and a proximal end and having a sharpenedinsertion tip at the distal end, the needle being positioned within thedistal end portion of the longitudinal duct of the cannula with theinsertion tip extending beyond the distal end of the cannula; and

a catheter inserter having inserter distal and proximal ends and havinga cannula guide channel extending from the inserter distal end to theinserter proximal end, the cannula being positioned in slidablerelationship through the channel such that the distal end portion of thecannula extends beyond the distal end of the channel; and

a means for selectively restricting the cannula and needle from slidingrelative to the channel;

(b) positioning the inserter on the cannula such that the desired lengthof the distal end of the cannula extends beyond the distal end of thechannel;

(c) engaging the means such that the cannula and the needle arerestricted from sliding relative to the channel;

(d) inserting the needle and the cannula partially into the livingsubject.

Yet another aspect of the invention relates to a catheter assemblycomprising:

a cannula having a distal end portion, a proximal end portion, and alongitudinal duct therethrough from the proximal end portion to thedistal end portion, the cannula being formulated of a material selectedsuch that an outer circumference thereof increases when at least a partof the distal end portion thereof is inserted into a living subject andmaintained in said living subject, and/or when the duct is contacted byan aqueous liquid, for a period of time sufficient for the increasedouter circumference to form;

an inserter having a guide channel therethrough in which the cannulaslidably fits when the cannula has the smaller outer circumference andby which the cannula is non-slidably held when the cannula has theincreased outer circumference; and

means for selectively restricting the cannula from sliding relative tothe channel when the cannula has the smaller outer circumference.

Still another aspect comprises a catheter assembly comprising:

a cannula having a distal end portion, a proximal end portion, and alongitudinal duct therethrough from the proximal end portion to thedistal end portion, the cannula being formulated of a material selectedsuch that it has a 2.5% secant modulus which decreases

(a) on exposure to temperature of from about 20° C. to about 40° C.;and/or

(b) upon insertion of a part of the distal end portion of the cannulainto a body of a living subject and maintained therein; and/or

(c) when the duct of the cannula is contacted by a liquid, for a periodof time; such that the cannula softens with a softening ratio of atleast 2:1;

an inserter having a guide channel therethrough in which the cannulaslidably fits; and

means for selectively restricting the cannula from sliding relative tothe channel when the cannula has the smaller outer diameter.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a perspective view of a catheter assembly of the inventionwith a slidable inserter having preferred embodiments including a hub,penetrable polymeric sealing member over one proximal end of the hub andan additional port for introduction or withdrawing of liquids.

FIG. 2 is a perspective view of another embodiment of the inventioncomprising a hub, slidable inserter, cannula and needle.

FIG. 3 is a cross-sectional view of the catheter assembly through thecatheter inserter.

FIG. 4 is a cross-sectional view of the catheter assembly through thecatheter inserter which is engaged to restrict the cannula and needlefrom sliding relative to the inserter.

FIG. 5 is a cross-sectional view of the catheter assembly through thecatheter inserter with no needle and the outer diameter of the cannulawhich has increased to restrict the cannula from sliding relative to theinserter.

FIG. 6 is a cross-sectional view with an embodiment of a hub and cannulawhose outer circumference is capable of expanding.

FIG. 7 is a cross-sectional view similar to FIG. 6 but with the cannulain the expanded state.

FIG. 8 is a perspective view of a portion of a catheter assembly showinga further embodiment of the invention wherein a portion of the cannulais covered with a protective sheath.

FIG. 9 is a view similar to FIG. 8 but with the sheath in the process ofremoval.

FIG. 10 is a perspective view of a complete catheter assembly similar toFIG. 9 where the sheath has indicator markings for insertion depth.

DETAILED DESCRIPTION OF THE INVENTION

The catheter assembly of the invention comprises a cannula of a desiredlength, a needle and a slidable inserter. In a preferred embodiment, thecatheter assembly comprises a cannula of a desired length with an outercircumference which increases, and/or of a material whose 2.5% Secantmodulus decreases, and a slidable inserter and optionally a protectivesheath.

The cannula of the invention can be any material suitable forintroduction into a living subject. Preferably these materials arepolymeric in nature and are selected to be sufficiently stiff forinsertion but still relatively flexible such as fluoroethylene propylene(e.g. FEP-TEFLON from DuPONT) or the like. In general, the cannulashould have a 2.5% Secant Modulus greater than about 20,000 N/cm² andpreferably greater than about 28,000 N/cm² to prevent buckling orwrinkling upon insertion into the subject. Even more preferred are thosecompositions which soften or exhibit a decreased 2.5% Secant Modulus forexample by exposure to liquids or upon insertion of the distal endportion of the cannula into the body of a living subject and maintainedtherein or upon exposure to a temperature of from about 20° C. to about40° C. Particulary preferred compositions absorb liquid (e.g. hydration)and thereafter soften to a 2.5% Secant modulus of less than 7,000 N/cm²which reduces the trauma to the surrounding tissues of the subject. Theterm softening ratio is used herein to refer to the ratio of the 2.5%Secant modulus values of the composition selected in the form of atubular cannula initially to the 2.5% Secant modulus of the compositionwhen softened. It is preferred that at least a portion of suchcompositions are hydrophilic. It is also preferred that the compositionsoften with a softening ratio of at least about 2:1.

Examples of softening polymers useful in the practice of the inventionare those described in commonly assigned copending application serialnumber 780,543 filed Sept. 26, 1985, incorporated herein by reference.The preferred composition for the cannula comprises

(a) a first phase which comprises a substantially nonhydrophilicpolymeric component; and

(b) a second phase which comprises a hydrophilic polymeric component;

said material (i) being capable of absorbing water to an extent that itsoftens with a softening ratio of at least about 2:1 and/or swells witha swelling ratio of at least about 1.3:1; and (ii) when substantiallycompletely hydrated, having an energy to break of at least about 700N-cm/cm³ and a 2.5% Secant Modulus of less than about 7,000 N/cm².

Also useful are those softening polymers, described in U.S. Pat. Nos.4,359,558, 4,424,305, 4,454,309 and 4,439,583 to Tyndale Plains-HunterLtd. incorporated herein by reference. The preferred cannula compositionessentially comprises a polyurethane diacrylate composition having fromabout 90 to about 65 weight percent of a hydrophilic polyurethane resinand from about 10 to about 35 weight percent of a diacrylate.

An alternative material which may be utilized as the cannula material isa thermoplastic composition with softenable and/or shape-memoryproperties. Such polymeric compositions are described, for example, inthe following articles: Softenable, Shape-Memory Thermoplastics ForBiomedical Use, Robert S. Ward, MD7D, August 1985; and Thromboresistant,Radiopaque, Softenable Thermoplastic Catheter Compound With Shape-MemoryProperties, R. S. Ward, K. A. White, J. S. Riffle, Second World CongressOn Biomaterials, 10th Annual Meeting Of The Society For Biomaterials,Washington, D.C., April 27-May 1, 1984. The aforementioned thermoplasticcompositions comprise a base polymer that is a block or segmentedco-polymer thermoplastic with at least one block type which has anabrupt effective glass transition temperature (T_(g)) at or greater thanroom temperature, but less than approximately body temperature. Theremainder of the base polymer contains hard blocks whose dominantthermal transition is substantially greater than body temperature. Thecannulae can also be made to expand and soften as follows. The cannulaeare originally made with their eventually desired expanded internaldiameter and then are heated above the glass transition (T_(g)), drawnout to form longer and thinner cannulae and held in this state untilcooled below the (T_(g)). Once the longer and thinner cannulae havewarmed to a temperature that is greater than room temperature but lessthan approximately body temperature, i.e., once the cannulae havereached the glass transition temperature, (T_(g)), the shape-memoryproperties operate and the cannulae increase in internal and externaldiameter while shrinking in length.

It is also preferred when selecting such softening materials thatcannulae of such material also swell wherein at least a portion of thecannula inner cross-section of the duct and/or outer circumference ofthe cannula increases to form an enlarged inner cross-section of theduct and/or enlarged outer circumference of the cannula when inserted ina living subject and maintained therein and/or when the duct iscontacted by a liquid for a period of time sufficient for the enlargedduct cross-section and/or outer circumference to form. Preferably theduct cross-section increases to from about 25% to about 400%.

The composition of the cannula may be crosslinked if desired.Crosslinking gives the composition strength above the melting orsoftening points of the uncrosslinked polymeric components permittingsterilization of the catheter assembly using a cannula of suchcomposition at above such temperature. Crosslinking of the materialselected for the cannula may also be used to adjust the 2.5% secantmodulus of the composition to a desired value. Crosslinking may alsoincrease the tensile energy to break of the material which has beensoftened. Cross-linking can also be used to minimize extractablecomponents of the composition.

Crosslinking can be effected by use of an appropriate crosslinking agentor by irradiation, preferably in the presence of a crosslinkingpromoter, such as triallyl isocyanurate or the like. In a preferredembodiment the material is crosslinked by high energy gamma or betaradiation.

The material of the cannula may contain additional ingredients such asstabilizers, antioxidants, radiopacifiers, medicaments, fillers or thelike. For certain applications it may be advantageous to incorporate awater soluble or water dispersable medicament which can leach from thematerial when it contacts the fluids of the living subject. Suchmedicaments include anti-thrombogenic agents, antibiotics, antiviralagents, anticoagulants, anti-inflammatory agents or the like.

A cannula selected such that it swells or softens should not do soappreciably during the time it is being inserted in a living subject orthe like. It is preferable that such swell or softening time shouldpreferably be at least about 15 seconds and preferably at least about 60seconds. The swelling of the cannula has several advantages. Swelling ofthe cannula permits insertion of a smaller device for equivalent fluidflow and/or can result in pressure around a wound site reducing bleedingand bacterial invasion into the wound and prevent catheter slipout, acommon cause for changing catheters prematurely. Increased cross-sectionof the cannula duct also permits increased flow through the cannula whencompared with similar non-swelling cannula of identical initialdimensions. This allows access to smaller areas such as the veins in thelimbs and easier insertion into the selected site. Further, swelling ofthe cannula may increase the outer circumference sufficiently that itbecomes as great as the diameter of the inserter channel. Afterinsertion of the cannula this may be desirous. The inserter then losesits ability to slide relative to the cannula and needle due to thepressure of the cannula against the inserter channel. This isadvantageous in preventing relative movement of the cannula or inserter.Once the inserter is attached (e.g. by taping) to the subject, furthermovement of the cannula in or out of the subject is limited. Cannulaewhich become soft are also advantageous. A soft cannula tends to causeless irritation to the, intima (lining of the vein), to the insertionsite and is less likely to contribute to mechanical phlebitis. Thesoftness of the cannula also permits it to float in a vein rather thanlie on the point where inserted and consequently any infusion isdelivered evenly helping to avert chemical phlebitis.

Once the cannula is selected, a needle is selected having a distal andproximal end and having a sharpened insertion tip at the distal end. Theneedle may be selected to be either hollow or solid. The needle ispositioned within the distal end portion of the longitudinal duct of thecannula with the insertion tip extending beyond the distal end of thecannula. An extraction wire, rod, etc. may optionally be attached to theproximal end of the needle and extend outward to the proximal end of thecannula. Extraction of the needle may be accomplished by pulling on theextraction wire. Alternately, the proximal end of the needle may extendbeyond the inserter toward the proximal end of the the cannula for easeof extraction.

Finally, a catheter inserter having distal and proximal ends and havinga cannula guide channel extending from the distal end to the proximalend of the inserter has a cannula positioned in slidable relationshipthrough the channel such that the distal end portion of the cannulaextends beyond the distal end of the channel. Means are provided forselectively restricting the cannula and needle from sliding relative tothe channel. In its preferred embodiment the catheter inserter comprisesa body having a pair of members extending therefrom, the members beingmovable to selectively restrict the cannula and needle from slidingrelative to the channel. In a more preferred embodiment the body has apair of flexible wing members extending therefrom, the wings beingfoldable upward together to selectively restrict the cannula and needlefrom sliding relative to the channel. In another more preferredembodiment the members are moved from a relaxed positioned to a tensedposition to selectively restrict the cannula and needle from slidingrelative to the channel. The body of catheter inserter will preferablyhave a bore extending from the distal end to the proximal end of theinserter and which serves as the guide channel. The diameter of theguide channel will preferably be at least equal to or slightly largerthan the outer circumference of the cannula. In any event, the cannulaand channel will be such that the cannula can be positioned in slidablerelationship to the channel. Preferred catheter inserters resemble thewinged inserters of the prior art but have relatively largerlongitudinal bores and comprise a continuous cannula extending beyondthe distal end of the inserter to beyond the proximal end of theinserter to allow a slidable relationship with the cannula. Otherinserters would include tubular devices with an enlarged bore forpositioning the cannula and an area which could be manually squeezed,have a hose clamp attached thereover, or have a means tightened thereonto restrict the cannula sliding relative to the channel. Another methodof obtaining the slidable relationship is to use an inserter such as aspring which is normally closed and prevents the slidable relationshipand must be opened to achieve the slidable relationship.

In particular, the catheter assembly of the invention is useful forinserting a cannula in a living subject. Preferably the cannula isinserted in a blood vessel or cavity. The preferred use of the catheterassembly is for intravenous (IV) use. By living subject is meant anyliving thing, e.g. mammal, reptile, fish, etc. for which fluids arenecessary to infuse or drain. In particular the assembly is useful inmammals particularly, horses, cattle, dogs, cats and humans.

The catheter assembly may be used at this stage to infuse or drainliquids or to hook or connect to other apparatus or devices or used toposition sensors or the like.

In a preferred embodiment the catheter further comprises a cannula hubportion. The hub portion has a passageway therethrough from the proximalend to the distal end of the hub and has an attaching means forattaching the proximal end portion of the cannula to the distal end ofthe hub with the passageway in flow communication with the duct in theproximal end portion of the cannula. Many such hubs are known in theprior art and are suitable for the invention. Where the cannula materialis a swellable material it is desirable to have a hub assembly whichwill prevent restriction of flow in the cannula and will accommodate theexpansion. One such hub is described in commonly assigned U.S. patentapplication Ser. No. 788,461 filed Oct. 17, 1985, incorporated herein byreference.

Preferably the cannula hub portion has a hub portion having a hubpassageway therethrough from a first to a second end thereof, whereinthe hub passageway has a cross-sectional area throughout at leastsubstantially equal to the enlarged duct cross-section and which furthercomprises an attaching means for attaching the proximal end portion ofthe cannula to the first end of the hub with the passageway through thehub in flow communication with the duct in the proximal end portion ofthe cannula, the attaching being in a manner such that thecross-sectional area of the duct adjacent to the proximal end portion,following formation of the enlarged duct cross-section, is throughout atleast substantially equal to the enlarged duct cross-section along theremainder of the cannula.

The opening at the proximal end of the hub may be sealed by use of apenetrable polymeric sealing member. The sealing member will be usefulin preventing escape of fluids from the subject. Additionally, thesealing member can be used to introduce fluids for example by insertingthe needle of a syringe through the penetrable member. Yet another usefor a polymeric sealing member would be to prevent fluid loss when aneedle extraction wire is withdrawn from the proximal end of the hub.The hub portion may also be designed with any fitting or attachmentmeans for attaching tubing or the like in flow communication with thehub passageway (e.g. luer lock hub). It may also be desirous that morethan one opening in the proximal end of the hub will be in flowcommunication with the hub passageway (e.g. FIG. 1). This is useful toconnect one constant source of fluid (e.g. an IV drip bottle) and leavea different site accessible for single injection of additional fluid ormedicaments.

When a long section of cannula is to be inserted into the livingsubject, care must be used in maintaining sterility of the portion ofcannula initially positioned at the proximal end of the inserter.Contact of the cannula by the users fingers or the like wouldcontaminate the cannula making it unsuitable for use in a livingsubject. One solution to this problem is to enclose the proximal portionof the cannula that is to be handled in an axially collapsible cover forexample, a polyethylene bag of a very flexible material or a more rigidpolymeric material with accordian-type folds which allow axialcollapsing, such that the cannula may be inserted further by handlingthe cover.

Another solution to the problem is to cover a portion of the cannulawith an axially non-collapsible sheath. By axially non-collapsible ismeant that when pushing in the cannula for to further insertion whilealso grasping the sheath, the sheath does not buckle or wrinkle or thelike to an appreciable amount. The sheath, however, has walls which areof a relatively flexible material. The sheath has both a distal end anda proximal end. There is further, a longitudinal slit at least a portionof the way through the wall of the sheath. In another embodiment theslit does not extend all the way through the wall of the sheath prior toremoval to further aid in the protecting of the cannula. The cannula ispositioned within the duct of the sheath in the area to be protected.The sheath is capable of being opened along the longitudinal slit andremoved from the cannula. In a preferred embodiment there is a means foraiding in the opening of the longitudinal slit. This means may be a partof the inserter (as in FIG. 8) which opens the sheath during insertionof the cannula or an added device which opens the sheath duringinsertion. The inserter is preferably made of a polymeric material.Preferred polymeric materials include polyvinyl chloride (PVC),polyurethane and fluoroethylene propylene.

The sheath may further comprise indicators (FIG. 10) positioned suchthat upon insertion of the cannula and corresponding removal of thesheath the indicators indicate the depth to which the cannula has beeninserted.

Once the catheter assembly is selected and made, the method of theinvention may be used to insert the cannula into a living subject. Themethod further comprises positioning the inserter on the cannula suchthat the desired length of the distal end of the cannula extends beyondthe distal end of the channel. In general from about 12 mm to about 50mm of cannula will be so positioned for insertion. This may beaccomplished for example by sliding the inserter to the desiredposition. This is advantageous over fixed inserters which requirestocking of different desired lengths. Next the inserter means isengaged such that the cannula and the needle are restricted from slidingrelative to the channel. In the preferred embodiment this isaccomplished by folding the flexible wing members of the preferredinserter upward (see Figures) such that the inserter means is engaged.The needle and cannula distal ends may then be inserted into the livingsubject by grasping the inserter and pushing the needle into the desiredarea.

Once the cannula is inserted as desired the inserter means may bedisengaged. At this point it is desirous that the needle be removed toprevent any damage to the subject or cannula. The needle may bewithdrawn at least a portion toward and preferably out the proximal endportion of the cannula. This is preferably accomplished by pulling on anextraction wire attached to the proximal end of the needle as describedearlier.

The cannula may also be inserted further into the subject (beforeswelling where appropriate) by grasping the hub at the cannula in thearea between the proximal end of the cannula and the proximal end of theinserter and pushing in the direction of insertion. Where a protectivecover is used, the protective cover is grasped firmly enough to graspboth the cover and cannula for further insertion.

Once this is accomplished fluids may be drained or introduced into thesubject as desired, for example, wound drainage, IV drip bottles,syringe injection and the like.

Referring now to the drawings. FIG. 1 relates to a catheter assembly ofthe invention comprises cannula distal (1) and proximal (2) ends whichhave longitudinal duct (3) therein. Positioned in the longitudinal ductis a needle (4) having a sharpened end (5). Inserter (6) comprisingdistal end (7) and proximal end (8), has a bore (9) therethrough of adiameter about equal to or greater than the outer diameter of thecannula. The inserter also has a means for restricting the relativemovement of the cannula and needle relative to the inserter whichcomprises wings (10) which can be folded upward to be engaged. Theneedle also has extraction wire (18) attached to its proximal endextended out the penetrable polymeric member (14) to a knob (17) forgrabbing the wire. The hub (11) of FIG. 1 has a bore (12) from thedistal end (16) to the proximal end (13 and 19) in fluid communicationwith the cannula duct. Proximal end (19) can be used to introduce tubingand the like by removal of plug (15) in the proximal end passageway.

In FIG. 2, all the numbers refer to identical portions except that FIG.2 has a hub with only a single proximal end (13) in fluid communicationwith the cannula.

FIG. 3 is a cross-sectional view of the catheter inserter (6) with wingmembers (10) and bore (3) having cannula (1) and needle (4) positionedtherein.

FIG. 4 is similar to FIG. 3 except the wings (10) have been foldedupward to engage which restricts the cannula and needle from slidingrelative to the inserter.

FIG. 5 is similar to FIG. 3 except that the needle has been removed andthe cannula has swollen such that its outer diameter is about equal tothe diameter of the bore.

Referring now to FIG. 6 and 7, there is illustrated a particularembodiment of the present invention which includes a hub insert 342 foruse with an expanding cannula. In the embodiment in FIG. 6 the hubinsert has an opening 344 therethrough from a first end 346 to a secondend 348 thereof. The opening 344 has inner cross-section which isthroughout at lest substantially equal to 125% of the initial ductcross-section 324 and is preferably at least substantially equal to theenlarged duct cross-section (FIG. 7). A part 352 of the passageway 328in the hub 319 adjacent the first end 330 of the hub 314 has an innersurface which is geometrically similar to and positioned about an outersurface 356 of the hub insert 342. The part 352 of the passageway 328and the outer surface 356 of the hub insert 342 are adapted to hold theproximal end portion 318 of the cannula 312 impressed therebetween. Ifdesired, a bonding composition can be attached between the hub insert342 and the duct 322 and/or between the port 352 of the passageway 328and the outer surface of the proximal end portion 318 of the cannula312. FIG. 6 illustrates an embodiment wherein the cannula 312 is in thenon-expanded state and has not yet expanded. The proximal end portion318 of the cannula 312 has been positioned over the hub insert 342, thuspreshaping or preforming it only adjacent to the hub insert 342.Alternatively, the proximal end portion 318 may be thermally orotherwise preshaped if preferred. FIG. 7 illustrates the embodimentwherein the cannula is in the expanded state.

Referring to FIGS. 8 and 9 we see a portion of a perspective view of acatheter assembly with an inserter 6. On the cannula 404 is a protectivesheath 403 with a longitudinal slit 402 for removing the sheath 403. Inorder to help open the cannula along the longitudinal slit, a means 401is provided on the inserter such that on pushing the sheath towards themeans the sheath opens along the slit and is removed from the catheterassembly or further depicted in FIG. 9.

Referring to FIG. 10, we see an entire perspective view of a catheterassembly with protective sheath being removed as in FIG. 9. Theprotective sheath in FIG. 10 has additional indicators 405 whichindicate the depth to which the cannula has been inserted.

What is claimed is:
 1. A catheter assembly, comprising:a cannula havinga distal end portion, a proximal end portion, and a longitudinal ducttherethrough from the distal end portion to the proximal end portion; aneedle having a distal and a proximal end and having a sharpededinsertion tip at the distal end, the needle being positioned within thedistal end portion of the longitudinal duct of the cannula with theinsertion tip extending beyond the distal end of the cannula; a catheterinserter having inserter distal and proximal ends and having a cannulaguide channel extending from the inserter distal end to the inserterproximal end, the cannula being positioned in slidable relationshipthrough the channel such that the distal end portion of the cannulaextends beyond the distal end of the channel; and a means forselectively restricting the cannula and needle from sliding relative tothe channel;wherein at least a portion of the cannula is of a materialselected such that an outer circumference of the duct increases to forman enlarged outer circumference such that it restricts the cannula fromsliding relative to the channel when at least a part of the distal endportion of the cannula is inserted into a body of a living subject andmaintained therein and/or when the duct is contacted by a liquid, for aperiod of time sufficient for the enlarged outer diameter to form.
 2. Acatheter assembly, according to claim 1, wherein the cannula guidechannel comprises a bore extending from the distal end to the proximalend of the inserter.
 3. A catheter assembly according to claim 1,wherein the catheter inserter comprises a body having a pair of membersextending therefrom, the members being movable to selectively restrictor release the cannula and needle from sliding relative to the channel.4. A catheter assembly according to claim 1, wherein at least a portionof the cannula is of a material selected such that an innercross-section of the duct increases to form an enlarged duct crosssection when at least a part of the distal end portion of the cannula isinserted into a body of a living subject and maintained therein and/orwhen the duct is contacted by a liquid, for a period of time sufficientfor the enlarged duct cross-section to form.
 5. A catheter assemblyaccording to claim 4, wherein the inner cross-section of the ductincreases when the duct is contacted by an aqueous liquid.
 6. A catheterassembly according to claim 4, wherein the increase in the ductcross-section is from about 25% to about 400%.
 7. A catheter accordingto claim 4 which further comprises a cannula hub portion having a hubpassageway therethrough from a first to a second end thereof, whereinthe hub passageway has a cross-sectional area throughout at leastsubstantially equal to the enlarged duct cross-section and which furthercomprises an attaching means for attaching the proximal end portion ofthe cannula to the first end of the hub with the passageway through thehub in flow communication with the duct in the proximal end portion ofthe cannula, the attaching being in a manner such that thecross-sectional area of the duct adjacent the proximal end portion,following formation of the enlarged duct cross-section, is throughout atleast substantially equal to the enlarged duct cross-section along theremainder of the cannula.
 8. A catheter assembly according to claim 1,wherein at least a portion of the cannula is of a material selected suchthat it has 2.5% secant modulus which decreases(a) on exposure totemperature of from about 20° C. to about 40° C.; and/or (b) uponinsertion of a part of the distal end portion of the cannula into a bodyof a living subject and maintained therein; and/or (c) when the duct ofthe cannula is contacted by a liquid, for a period of time;such that thecannula softens with a softening ratio of at least 2:1.
 9. A catheterassembly according to claim 8, wherein the 2.5% secant modulus of thecannula decreases when the cannula is contacted by an aqueous liquid.10. A catheter assembly according to claim 8, wherein at least a portionof the cannula is selected of a material comprising a thermoplasticcomposition with an effective glass transition temperature of greaterthan room temperature but less than about the body temperature of theliving subject into which the cannula is to be inserted.
 11. A catheterassembly according to claim 10, wherein the thermoplastic compositionfurther has shape memory properties.
 12. A catheter assembly accordingto claim 1 which further comprises a cannula hub portion having apassageway therethrough from the proximal end to the distal end of thehub, and having an attaching means for attaching the proximal endportion of the cannula to the distal end of the hub with the passagewayin flow communication with the duct in the proximal end portion of thecannula.
 13. A catheter assembly according to claim 12, wherein the hubhas a penetrable polymeric sealing member positioned to seal theproximal end of the hub.
 14. A catheter assembly according to claim 12,wherein the hub has a connection means at the proximal end of the hubfor attaching tubings or fitting in flow communication with the hubpassageway.
 15. A catheter according to claim 12, wherein the needle oran extraction wire that is attached to the proximal end of the needleextends through the longitudinal duct of the cannula distally to the hubpassageway and out the proximal end of the hub.
 16. A catheter assemblyaccording to claim 15, wherein the hub has a connection means at theproximal end of the hub for attaching tubings or fittings in flowcommunication with the hub passageway.
 17. A catheter assembly accordingto claim 1, wherein the needle or an extraction wire attached to theproximal end of the needle extends through the longitudinal duct of thecannula and out the proximal end of the cannula.
 18. A catheter assemblyaccording to claim 1, wherein the distal end portion of the cannula isof a material having a 2.5% secant modulus greater than about 20,000N/cm².
 19. A catheter assembly according to claim 1, wherein at least aportion of the cannula is selected of a material comprising athermoplastic composition with an effective glass transition temperatureof greater than room temperature but less than about the bodytemperature of the living subject into which the cannula is to beinserted.
 20. A catheter assembly according to claim 19, wherein thethermoplastic composition further has shape memory properties.
 21. Acatheter according to claim 1, wherein the cannula comprises a materialwith hydrophilic properties.
 22. A catheter according to claim 21wherein the cannula comprises:(a) a first phase which comprises asubstantially nonhydrophilic polymeric component; and (b) a second phasewhich comprises a hydrophilic polymeric component;said material (i)being capable of absorbing water to an extent that it softens with asoftening ratio of at least about 2:1 and/or swells with a swellingratio of at least about 1.3:1; and (ii) when substantially completelyhydrated, having an energy to break of at least about 700 N-cm/cm³ and a2.5% Secant modulus of less than about 7,000 N/cm².
 23. A catheterassembly to claim 21, wherein the cannula comprises a graft or blockcopolymer with hydrophilic segments with a softening ratio of at least2:1.
 24. A catheter according to claim 23, wherein the cannula comprisesa polyurethane diacrylate composition having from about 90 to about 65weight percent of a hydrophilic polyurethane resin and from about 10 toabout 35 weight percent of a diacrylate.
 25. A method of inserting acatheter into a living subject comprising:(a) selecting a catheterassembly, comprising:a cannula having a distal end portion, a proximalend portion, and a longitudinal duct therethrough from the distal endportion to the proximal end portion; a needle having a distal and aproximal end and having a sharpened insertion tip at the distal end, theneedle being positioned within the distal end portion of thelongitudinal duct of the cannula with the insertion tip extending beyondthe distal end of the cannula; a catheter inserter having inserterdistal and proximal ends and having a cannula guide channel extendingfrom the inserter distal end to the inserter proximal end, the cannulabeing positioned in slidable relationship through the channel such thatthe distal end portion of the cannula extends beyond the distal end ofthe channel; and a means for selectively restricting the cannula andneedle from sliding relative to the channel; (b) positioning theinserter on the cannula such that the desired length of the distal endof the cannula extends beyond the distal end of the channel; (c)engaging the means such that the cannula and the needle are restrictedfrom sliding relative to the channel; and (d) inserting the needle andthe cannula partially into the living subject;wherein at least a portionof the cannula is of a material selected such that an outercircumference of the duct increases to form an enlarged outercircumference such that it restricts the cannula from sliding relativeto the channel when at least a part of the distal end portion of thecannula has been inserted into the living subject and maintained thereinfor a period of time sufficient for the enlarged outer diameter to form.26. A method according to claim 25, which further comprises the step ofdisengaging the inserter means.
 27. A method according to claim 25,which further comprises the steps of inserting the cannula further intothe living subject to the desired length.
 28. A method according toclaim 25, wherein the cannula is a material selected such that it has2.5% secant modulus which decreases.(a) on exposure to temperature offrom about 20° C. to about 40° C.; and/or (b) upon insertion of a partof the distal end portion of the cannula into a body of a living subjectand maintained therein; and/or (c) when the duct of the cannula iscontacted by a liquid, for a period of time;such that the cannulasoftens with a softening ratio of at least 2:1.
 29. A method accordingto claim 25 which further comprises the step withdrawing the needle atleast a portion of the way toward the proximal end portion of thecannula.
 30. A method according to claim 29 wherein the needle iswithdrawn by pulling on an extraction wire attached to the proximal endof the needle.
 31. A method according to claim 25 wherein the insertercomprises a body having a pair of members extending therefrom, theinserter means being movable to selectively restrict or release thecannula and needle from sliding relative to the channel.
 32. A methodaccording to claim 25 wherein the cannula is of a material selected suchthat the outer circumference increases when at least a part of thedistal end portion of the cannula is inserted into a body of a livingsubject and maintained therein and/or when the duct is contacted by aliquid, for a period of time sufficient for the enlarged outercircumference to form such that it selectively restricts the cannulafrom sliding relative to the channel.
 33. A method according to claim 25wherein the cannula and the needle are inserted into a blood vessel of aliving subject.
 34. A method according to claim 25, wherein the cannulaand the needle are inserted into a cavity of a living subject.
 35. Amethod according to claim 25, including the added steps of:(e) attachingthe mechanical means to the living subject adjacent the point ofinsertion of the cannula; and (f) maintaining the distal end portion ofthe cannula partially in the living subject for a desired period oftime.